CFD Enhanced Thermal Spray Process for Coating of Cylinder Bores of Car Engines

Abstract

As the automotive industry shifts toward hybrid and alternative drive concepts like electromobility, it remains vital to continuously improve internal combustion technology. Internal combustion applications represent the largest portion of transportation technologies. Continuous development and improvement of passenger car engines focus on reducing emission by weight reduction and enhanced efficiency. To gain a competitive advantage in present and future engines, Mercedes-Benz AG developed the innovative NANOSLIDE Ò technology that uses thermal spray technology, i.e., twin wire arc spray, to coat the internal diameter of cylinder bores. Computational fluid dynamics (CFD) simulation is utilized to investigate the complex gas flow in the cylinder bore of the crankcase during the coating process. Extensively experiments are performed and analyzed to compare the results with the quantitative analysis in order to enhance the properties of the cylinder coating. The combination of simulation and coating experiments led to the development of uniform distributed layer adhesion strength throughout the length of the cylinder bore.

Thermal wave interferometry measurements and microstructural analysis of twin wire arc spray cylinder coatings for passenger car engines

“…As Schilder et. al [3] presented in their work, the occurrence of lateral splat interfaces depends on process parameters of the twin wire arc spraying. Since the shape of the crankcase, Nitrogen gas flow, extraction velocity and other process parameters cause turbulences within the crankcase, the Oxygen content of the spray jet depends on the burner position in the crankcase.…”

“…Since the shape of the crankcase, Nitrogen gas flow, extraction velocity and other process parameters cause turbulences within the crankcase, the Oxygen content of the spray jet depends on the burner position in the crankcase. Schilder et al [3] used computational fluid dynamics (CFD) simulations as well as coating experiments to compare the Oxygen mass fraction at crankcase positions 20 mm and 100 mm. They found a significantly higher oxygen percentage at position 20 mm compared to 100 mm.…”

“…Additionally, to avoid contamina tion of the cylinder coating due to excessive particles and to lower the oxygen content within the spray jet, the atmosphere within the crank case is extracted continuously during the coating process. Computa tional fluid dynamic (CFD) simulations of the complex gas flow during the coating process as well as coating experiments have shown that the mass fraction of Oxygen in the atmosphere surrounding the spray jet strongly influences the lamellar structure [3]. Higher mass fraction of Oxygen leads to enhanced oxidation of the spray particles and therefore increases the amount of splat interfaces in the coating.…”

“…Higher mass fraction of Oxygen leads to enhanced oxidation of the spray particles and therefore increases the amount of splat interfaces in the coating. If Oxygen is banned almost entirely during the coating process, rather dense ther mally sprayed coatings with very few splat interfaces may appear [3,4,18].…”

“…Durability and life long integrity of thermally sprayed cylinder bore coatings are two mandatory aspects concerning the functionality of combustion engines and depend among others on the coatings' mechanical properties and microstructural characteristics. Binding errors, splat interfaces, and pores define decisive defects of the material influencing its' mechanical properties, which may be influenced by thermal spray parameters [3,4]. In terms of process monitoring a non destructive and non contact evaluation of these features with a short feedback loop is highly de sired.…”